All wheel drive (AWD) vehicles with a drivetrain topology including a Transfer Case with a selectable low range gear have existed on the market for many years. In the simplest form the low range gear is selected with an additional shift lever. In modern vehicles there is an increasing need for controllability and functionality of the low range gear. Such requirements can include the ability to “shift on the move”, i.e. the possibility to change low/high range without a complete stand-still of the vehicle. It's also desirable that the shifting of low/high range can be performed without actuating the AWD clutch at the same time, as that might influence the vehicle behavior negatively, as for example locking up the front and rear axle in a parking maneuver.
To meet the new requirements the shifting is normally controlled by an actuator rather than a manual lever. When combined with controllable AWD, such systems tend to be complex, heavy and include several actuators, mechanisms and sensors.
There are existing electromechanical systems utilizing just one actuator for both shifting and clutch actuation. The drawback of these electromechanical systems are that they tend to by heavier, be less flexible for packaging, have worse torque accuracy and controllability, need a more complex control strategy and have a higher peak current consumption.
There are also prior art hydraulic solutions as shown in FIG. 1, illustrating an example of an existing hydraulic solution for 2-Speed Transfer Cases using a pressure controlling pump, like e.g. a pump as described in WO2011043722, for both shift actuation and AWD clutch actuation. The drawbacks of this design are that the design tend to utilize multiple actuators which results in higher cost, weight and packaging size. Normally they are also designed with a slide valve which requires high cleanliness and an oil filter.